Burner for heating system

ABSTRACT

A burner for a furnace includes an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The burner further includes an outer wall which, defines an annulus for the fuel flow to the plurality of inner wall openings. An igniter is located in the central chamber. A furnace includes a heat exchanger and one or more burners disposed at and aligned with one or more burner openings of the heat exchanger. The one or more burners include an inner wall defining a central burner chamber. The inner wall includes a plurality of inner wall openings to admit a fuel flow into the central burner chamber. The one or more burners further include an outer wall defining an annulus for the fuel flow to the plurality of inner wall openings.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. provisional application Ser.No. 61/521,143, filed Aug. 8, 2011, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to heating systems. Morespecifically, the subject disclosure relates to burners for residentialand commercial heating systems.

Heating systems, in particular furnaces include one or more burners forcombusting a fuel such as natural gas. Hot flue gas from the combustionof the fuel proceeds from the burner and through a heat exchanger. Thehot flue gas transfers thermal energy to the heat exchanger, from whichthe thermal energy is then dissipated by a flow of air driven across theheat exchanger by, for example, a blower.

A typical construction is shown in FIG. 1. A burner 100 is locatedexternal to a heat exchanger 102. The burner 100, referred to as aninshot burner 100, receives a flow of fuel from a fuel source 104. Anignition source 106 combusts the flow of fuel. Even though the inshotburner 100 is in close proximity to heat exchanger 102, surfaces of theheat exchanger 102 adjacent to the combustion flame 110 are keptrelatively cool by a flow of secondary air 108 to prevent damage to thesurfaces of the heat exchanger 102 via the combustion flame 110.

Another type of burner is a premix burner in which fuel and air aremixed in the burner nozzle prior to injection into a combustion zone 112where the ignition source 106 ignites the mixture. Premix burners,compared to inshot burners, emit much lower levels of NO_(x), theemissions of which are tightly regulated and restricted. Because of thisadvantage of premix burners, it is appealing to introduce premix burnersinto furnaces. A premix burner having physical and operatingcharacteristics similar to the burner 100 would not be suitable for usewith heat exchanger 102. The heat exchanger walls would necessarily bein close proximity to the burner and thus the concentration of heatproduced in the immediate vicinity of the burner would result inexcessively high temperatures in the wall of the heat exchanger 102.Such high temperatures would increase the surface temperatures of thesurrounding heat exchanger 102 and shorten the life of the heatexchanger 102. Further, premix burners have a much quicker heat releasethan inshot burners and do not have the benefit of secondary airflow toprotect the heat exchanger surfaces from damage. Thus, simply replacinginshot burners with premix burners in an existing furnace constructionwould result in excessively high temperatures at adjacent heat exchangersurfaces. Further, ignition access to a premix burner surface can bedifficult and result in even more energy being dumped into the heatexchanger entry surfaces.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a burner for a furnaceincludes an inner wall defining a central burner chamber. The inner wallincludes a plurality of inner wall openings to admit a fuel flow intothe central burner chamber. The burner further includes an outer wallwhich, together with the inner wall, defines an annulus for the fuelflow to the plurality of inner wall openings. An igniter is located inthe central chamber.

According to another aspect of the invention, a furnace includes a heatexchanger and one or more burners disposed at and aligned with one ormore burner openings of the heat exchanger. The one or more burnersinclude an inner wall defining a central burner chamber. The inner wallincludes a plurality of inner wall openings to admit a fuel flow intothe central burner chamber. The one or more burners further include anouter wall, together with the inner wall defining an annulus for thefuel flow to the plurality of inner wall openings. An igniter is locatedin the central chamber.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a typical burner arrangement;

FIG. 2 is a schematic view of an embodiment of a furnace; and

FIG. 3 is a cross-sectional view of an embodiment of a burner.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 2 is an improved furnace 10. The furnace 10 includes aheat exchanger 12 with one or more burners 14 aligned with respectiveburner openings 60 in heat exchanger 12 walls 16. In some embodiments,the burners 14 are located substantially within the heat exchanger 12,while in other embodiments, the burners 14 may abut the heat exchanger12. In still other embodiments, the burners 14 offset a distance fromthe heat exchanger 12, but are aligned with the burner openings 60 suchthat, once ignited, the burners 14 radiate hot flue gas 18 into the heatexchanger 12, thermal energy from which is transferred to the heatexchanger 12 structure. The thermal energy is then dissipated from theheat exchanger 12 via a flow of air 20 driven across the heat exchanger12 by, for example, a blower 22. The heated flow of air 20 is deliveredthrough one or more ducts 24 to provide heating to a space 26, such as aroom or a building.

Referring now to FIG. 3, the burner 14 is substantially cylindrical inshape, and includes an outer wall 28 and an inner wall 30. It is to beappreciated that while a substantially cylindrical burner 14 is shown,it is merely exemplary. The burner 14 may have another cross-sectionalshape, for example, elliptical, conical, parabolic, partially circular,or the like. Both the inner wall 30 and the outer wall 28 may besubstantially cylindrical and in some embodiments are coaxial about acentral burner axis 32. The inner wall 30 defines a central chamber 34,and together with the outer wall 28 defines a burner annulus 36 betweenthe inner wall 30 and the outer wall 28. An igniter 38 for the burner islocated in the central chamber 34 and, in some embodiments, extendsalong the burner axis 32. The igniter 38 is located, for example, at aclosed end 52, or upstream end, of the burner 14. Further, in someembodiments, a flame sensor 40 is located in the central chamber 34, andalso may be located at the closed end 52.

The inner wall 30 includes a plurality of inner wall openings 42, and insome embodiments, may be at least partially a mesh screen. In someembodiments, the inner wall 30 is a unitary, replaceable component.Replacing the inner wall 30 at the end of its service life extends theoverall useful life of the burner 14. A flow of fuel 44 and a flow ofcombustion air 46 are delivered to the burner annulus 36 where they arepremixed. The air/fuel mixture 48 then flows through the inner wallopenings 42 or screen and into the central chamber 34 where the mixture48 is ignited. The flue gas 18 is emitted from the burner 14 at a distalend 50 of the central chamber 34 and into the heat exchanger 12structure.

The structure disclosed herein allows for the utilization of a premixburner 14 which reduces NO_(x) emissions compared to inshot burners,while not subjecting the heat exchanger 12 surfaces to direct effects ofthe combustion to prevent thermal damage to the heat exchanger 12. Thecylindrical structure of the burner 14 captures the combustion thermalenergy before it is emitted from the burner 14. Further, the burner 14is sized and configured to allow for the presence of the igniter 38 andflame sensor 40 within the burner 14 structure. This results in a spacesavings for the burner 14 and heat exchanger 12, thus allowing for anincreased cross-sectional sized burner 14 for a given heat exchanger 12cross-sectional size. Further, the flow through the burner annulus 36isolates the flame from the heat exchanger 12 and aids in cooling theheat exchanger 12 surfaces near the burner 14.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A burner for a furnace comprising: an inner wall defining a centralburner chamber, the inner wall including a plurality of inner wallopenings to admit a fuel flow into the central burner chamber; an outerwall, together with the inner wall defining an annulus for the fuel flowto the plurality of inner wall openings; and an igniter disposed in thecentral chamber.
 2. The burner of claim 1, wherein the inner wall atleast partially comprises a mesh screen defining the plurality of innerwall openings.
 3. The burner of claim 1, wherein one or more of theinner wall and the outer wall are substantially cylindrical.
 4. Theburner of claim 1, wherein the inner wall and the outer wall aresubstantially concentric about a burner central axis.
 5. The burner ofclaim 1, wherein the igniter is disposed at a closed end of the burner.6. The burner of claim 1, further comprising a flame sensor disposed inthe central burner chamber.
 7. The burner of claim 1, wherein the burneris alignable with a respective burner opening at a heat exchanger of afurnace.
 8. The burner of claim 1, wherein the plurality of inner wallopenings are configured to convey a mixture of air and fuel into thecentral burner chamber.
 9. The burner of claim 1, wherein the inner wallis a replaceable element.
 10. A furnace comprising: a heat exchanger;one or more burners disposed at and substantially aligned with one ormore burner openings of the heat exchanger, the one or more burnersincluding: an inner wall defining a central burner chamber, the innerwall including a plurality of inner wall openings to admit a fuel flowinto the central burner chamber; an outer wall, together with the innerwall defining an annulus for the fuel flow to the plurality of innerwall openings; and an igniter disposed in the central chamber.
 11. Thefurnace of claim 10, wherein the inner wall at least partially comprisesa mesh screen defining the plurality of inner wall openings.
 12. Thefurnace of claim 10, wherein one or more of the inner wall and the outerwall are substantially cylindrical.
 13. The furnace of claim 10, whereinthe inner wall and the outer wall are substantially concentric about aburner central axis.
 14. The furnace of claim 10, further comprising aflame sensor disposed in the central burner chamber.
 15. The furnace ofclaim 10, wherein the igniter is disposed at a closed end of the burner.16. The furnace of claim 10, wherein the inner wall is a replaceableelement.
 17. The furnace of claim 10, wherein the plurality of innerwall openings are configured to convey a mixture of air and fuel intothe central burner chamber.
 18. The furnace of claim 10, wherein thermalenergy of a flue gas emitted by the one or more burners is transferredto the heat exchanger.